Yellowstone River Wetland/
Riparian Change Detection
Pilot Study
Prepared for:
The Custer County Conservation District
and
The Yellowstone River Conservation District Council
By:
Gregory M. Kudray and Thomas Schemm
Montana Natural Heritage Program
Natural Resource Information System
Montana State Library
July 2006
MONTANA
Natural Heritage
Program
Yellowstone River Wetland/
Riparian Change Detection
Pilot Study
Prepared for:
The Custer County Conservation District
and
The Yellowstone River Conservation District Council
Agreement Number:
YRCDCOll
By:
Gregory M. Kudray and Thomas Schemm
MONTANA
Natuial Heritage
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© 2006 Montana Natural Heritage Program
P.O. Box 201800 • 1515 East Sixth Avenue • Helena, MT 59620-1800 • 406-444-5354
This document should be cited as follows:
Kudray, Gregory, M. and Thomas Schemm. 2006. Yellowstone River Wetland/Riparian Change
Detection Pilot Study. A report to the Custer County Conservation District and the Yellowstone River
Conservation District Council . Montana Natural Heritage Program, Helena, Montana. 16 pp. plus
appendices.
Executive Su m m a r y
Two reaches of the Yellowstone River riparian
corridor were mapped using the U.S. Fish and
Wildlife Service (USFWS) classification systems
for wetlands and Western riparian types. We used
two series of aerial photography (1950 and 2001) to
map all of this area and also mapped the upstream
reach A16 on two additional series (1976 and
1996). We evaluated but did not map a few photos
from the earliest series available (1937 and 1938)
for their suitability to map wetlands. Our primary
objective was to evaluate the feasibility of mapping
wetlands and tracking wetland change over time on
historical aerial photography. Government Land
Office (GLO) notes from the original land survey in
early settlement times were also reviewed to
determine if they could be used as a data source.
All photo series were suitable for mapping
wetlands although the 1950 photos for the A16
reach near Columbus had been acquired during a
date of very high water levels resulting in a
probable under mapping of Palustrine wetlands.
The 1950 photos were also of relatively poor
quality compared to all other series and some
vegetation classes could not always be reliably
discriminated. Any future wetland change project
should make sure that the dates of imagery are
comparable.
The riparian corridor is extremely dynamic, as are
the associated wetlands, which are created and
destroyed regularly. Evaluating wetland change
requires a large enough sample or total area
acreage summary to be meaningful.
Created ponds have increased in both reaches but
especially in the more developed reach near
Glendive (D6). Wetland acreage has decreased in
both reaches (-7.6%) with a greater decrease in
D6 (-11%). Natural wetlands have decreased
even more due to the acreage of created ponds
added. The less developed A16 reach was mapped
on four dates of aerial photography; wetland totals
varied within about a 10% range. The Riverine
type varied the most, probably due to water levels
and scouring from events within a few years
previous to the photo date.
Large peak flows are important in creating wetland
sites. There may be more wetland change
downstream than upstream since peak flows have
diminished more downstream.
The GLO notes can be used to quantify early
settlement riparian vegetation and compare it to
current conditions but wetlands are not
distinguished.
We created a crosswalk to the USFWS wetland
and riparian systems from Natural Resource
Conservation Service (NRCS) land use and
vegetation cover classification systems used for
mapping on the river. The relationship was typically
complex and the NRCS minimum mapping unit is
too large to identify the small wetlands often
present.
m
Acknowledgements
We gratefully acknowledge funding and other
support from the Custer County Conservation
District and the Yellowstone River Conservation
District Council. We also thank several others from
the Technical Advisory Committee who provided
support and many good ideas: Stan Danielsen, Greg
Johnson, George Jordan, Eric Laux, and Burt
Williams. We are grateful to Kevin Bon, National
Wetland Inventory, for his quality control help.
Special thanks to Jim Robinson, with his knowledge
and help with historical aerial photography along
the Yellowstone and especially Warren Kellogg, our
project contact who assisted the project in every
way.
IV
Tableof Contents
Introduction 1
Methods 2
Results and Discussion 4
Methodology 4
Wetland and Riparian Change from 1950 to 2004 4
Government Land Office Survey Notes Analysis 9
Crosswalk Between NRCS and USFWS Cover Types 9
Conclusions and Recommendations 15
References Cited 16
LisTOF Tables
Table 1. Wetland and riparian acreage for the A6 and D16 reaches combined 4
Table 2. River flow data from measuring stations closest to each mapped reach 5
Table 3. Wetland and riparian acreage for the A16 reach near Columbus 5
Table 4. Wetland and riparian acreage for the D6 reach near Glendive 5
Table 5. Length (m) of vegetation types compiled from GLO survey notes and 2001 mapping 9
Table 6. Crosswalk of NRCS land use cover types with USFWS wetland and riparian types 11
Table 7. Crosswalk of NRCS vegetation cover types with USFWS wetland and riparian types 13
List OF Figures
Figure 1. Map of study reaches of the Yellowstone River 3
Figure 2. Habitat change in the Yellowstone River reach A 16 near Columbus from 1951 to 2001 6
Figure 3. 1950 and 2001 mapping near Glendive 7
Figure 4. Annual peak Yellowstone River flows at Billings, MT near study reach A16 8
Figure 5 . Annual peak Yellowstone River flows at Sydney, MT near study reach D6 9
Figure 6. Section lines coded from GLO survey notes and 2001 mapping 10
Introduction
One hundred year flood events on the Yellowstone
River during 1996 and 1997 threatened human
constructed features and caused channel changes
and large-scale erosion. Over 100 permit applica-
tions were subsequently filed to armor or otherwise
modify riverbanks. Environmental groups contested
some permits. The controversy led to the authori-
zation of a comprehensive cumulative effects study
on the entire river. The federal study is led by the
Corps of Engineers with the Yellowstone River
Conservation District Council (YRCDC) as the
local partner. The goal of the Yellowstone River
Cumulative Effects Investigation is to acquire a
working knowledge of the dynamics of the Yellow-
stone River and its associated riparian area, the last
major free-flowing river in the lower forty-eight
States, to accurately predict cumulative effects
from natural processes and human effects, and to
develop best management practices.
changed in response to human and natural events
over the last several decades and wetlands are
important resources in this arid environment. Since
a study of the entire river corridor is a large project
and there is uncertainty about how well wetlands
could be mapped on historical aerial photography, it
was decided that a pilot study on two river reaches
would be used to make recommendations for the
techniques and materials that could be most effi-
ciently and accurately used to complete the larger
study. Our primary objective was to map wetlands
on two series of aerial photography 50 years apart,
evaluate the wetland/riparian change, and assess
three other dates of aerial photography for their
value in mapping these habitats. We also wanted to
review Government Land Office (GLO) notes from
the original Principal Base and Meridian survey to
evaluate how useful they would be in determining
early settlement vegetation patterns.
Several initial components of the cumulative effects
study have been funded including the acquisition of
bare earth Lidar (Light Detection and Ranging)
digital elevation mapping, geomorphic channel
classification, avian abundance and richness, land
use and cover mapping and historic aerial photo
coverage (see http://nris.mt. gov/yellowstone/ for
data and reports). However, there has been no
comprehensive work about how wetlands have
Another objective was to review the NRCS land
use and vegetation cover classification systems
now used in the Yellowstone River Corridor Cumu-
lative Effects Study and create a hierarchical
crosswalk with the wetland and riparian mapping
types. The NRCS systems will be evaluated for
usefulness in any future wetland or riparian change
analysis.
Methods
Wetland and riparian areas within two Yellowstone
River study reaches, A16 near Columbus, MT and
D6 near Glendive, MT (Figure 1) were mapped on
two dates of aerial photography: 1949(A16)/
1951(D6) black and white (referred to in this report
as 1950) and 2001 color infrared. The A16 reach
was also mapped on 1976 and 1996 black and white
photos. We evaluated but did not map a few photos
from the earliest series available (1937 and 1938)
for their suitability to map wetlands.
The wetlands were mapped with the National
Wetland Inventory (NWI) system (Cowardin et al.
1979). The USFWS Western Riparian System
(USFWS 1997) was used for riparian areas. Since
we were not mapping the surrounding uplands we
needed a boundary for mapping. The Lidar acquisi-
tion corridor. Corps of Engineers floodplain maps,
and the valley bottom delineation were assessed
(see http://nris.mt.gov/yellowstone for this data).
The valley bottom delineation was the most ecologi-
cally comprehensive representation of the riparian
corridor and was chosen as the mapping boundary.
The USFWS National Standards and Quality
Components for Wetlands, Deep water, and Related
Habitat Mapping (USFWS 2004) guided the
mapping techniques and Kevin Bon, the USFWS
Regional Wetlands Coordinator, participated in map
review and quality control. The digitized and
georeferenced aerial imagery was viewed on the
screen along with the Lidar digital elevation data.
Wetland and riparian polygons were digitized with
ESRI ArcMap software into the NWI master
geodatabase clipped for the study area. Since the
original NWI mapping from the 1980's had never
been digitized, we obtained the aerial photographs
with inked wetland delineations to use as an
ancillary data source.
We evaluated two wetland/riparian change detec-
tion techniques. One was a GIS based summary of
results from the total mapping dataset while the
other proposed a random selection of individual
wetland/riparian polygons to be followed over time.
The Yellowstone riparian corridor is so dynamic that
individual wetland/riparian polygons are often
altered naturally over the decades considered so we
concluded that the total GIS based summary would
give more accurate results than the other method.
The GLO survey notes recorded general vegetation
cover types at distances along the section lines they
traversed. We displayed the types along section
lines within some of the study area. Type distances
were compared with similar types from the most
current mapping.
dney
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Figure 1. Map of study reaches of the Yellowstone River
Results and Discussion
Methodology
A primary goal of this study was to determine if
wetlands could be mapped accurately from digitized
historical aerial photography. Of the five time series
evaluated only the 1950's series was problematic.
While we could map wetlands on these photos, we
found that the image quality was poorer than all
other photos including the earliest photos from the
late 1930's. Additionally, unlike the summer acquisi-
tion dates of the rest of the photography these
photos were taken during mid-May for the A16
reach when the river level was very high. Some
low wetlands were likely flooded at this time and
would have been mapped as a Riverine wetland
type instead of the correct type.
The dynamic nature of the riparian corridor results
in a regular cycle of wetland creation and destruc-
tion. Human or natural events at a given location
may destroy or create wetlands at that location and/
or have impacts further downstream. Following
individual wetland polygons over time will not give a
good indication of wetland change. A better ap-
proach is to either look at totals from entire areas or
sample at an intensity sufficient to represent the
area. We felt that the System level of the classifica-
tion (broad vegetation types like Forested or
Emergent Vegetation) could be mapped on the
historical photos with an accuracy suitable to
determine wetland and wetland type change over
time, although some types, like the closely related
Forested and Scrub-Shrub, may need to be com-
bined, especially on low quality photos (i.e. 1950's).
Grouping all wetlands together will be the most
accurate data.
Wetland and Riparian Change
From 1950 to 2004
Table 1 summarizes wetland and riparian area for
both reaches mapped. Differentiating some types
like Forested and Scrub-Shrub on the 1950's photos
was problematic. The total wetland and riparian
acreage declined by 195 acres (2.4%) There was a
decrease in wetland acreage of 354 acres (7.6%).
The decline in natural wetlands is greater because
there was an increase of 110 acres (>500%) in the
Palustrine Aquatic Bed acreage due to the creation
of sewage, stock, and recreational ponds. Also,
high water levels in the A16 1950's photos (Table
Table 1. Wetland and riparian acreage for the A6 and D16 reaches combined.
NWI Wetland or Riparian Type
1950
2001
Palustrine Aquatic Bed
25.4
135.7
Palustrine Emergent
163.5
231.0
Palustrine Scrub - Shrub
440.5
373.8
Palustrine Forested
62.0
59.8
Palustrine Wetland Total
691.4
816.4
Riverine Flowing
2254.7
2090.3
Riverine Bank
1712.9
1398.2
Riverine Wetland Total
3967.6
3488.5
Wetlands Total
4659.0
4304.9
Riparian Forested and Shrub
2927.2
3257.6
Riparian Total
3567.9
3727.4
Wetland and Riparian Total
8227.0
8032.4
Table 2. River fi
'ow data from measuring stations closest to each
mapped reach.
Photo Date
Flow at Photo
High Flow in Previous
Deviation From
Measuring
Date (cfs)
5 Years (cfs)
Average Peak
Station
8-26-1949
2,750
98,000
+50%
Sidney
5-17-1951
11,500
54,700
+32%
Billings
9-26-1976
6,210
69,500
+68%
Billings
8-24-1996
4,350
61,900
+49%
Billings
8-2-2001
7,610
82,000
+98%
Billings
8-2-2001
1,980
85,300
+30%
Sidney
2) probably covered some Palustrine wetlands. The
479 more acres of Riverine wetland (within the
channel) acres mapped in the 1950's supports the
theory that water was covering some normally
Palustrine wetlands in the photos.
The upstream reach A 16 was mapped with four
dates of aerial photography (Table 3). This
relatively undeveloped reach shows the inherent
variability of riparian wetlands over time (Figure
2), although total wetland acreage from all four
dates is within a 10% range. While Palustrine
wetland acreage was highest in 1950, the lowest
amount was mapped during the next time series
(1976), which also had the highest acreage of
Riverine wetlands. The only clear trend from this
mapping is the increase in ponds (Palustrine
Aquatic Bed) with time.
The downstream reach D6 includes Glendive and
shows considerable change in the wetland and
riparian resource (Table 4). The total wetland and
riparian area decreased by 528.3 acres (11%) with
395.2 less wetland acres (14%). Riverine bank
wetlands on shores, gravel bars, and similar fea-
tures showed a large decrease of 619 acres (46%).
Palustrine wetlands increased by 125 acres, most of
this is attributable to the 97.7 acres of increase in
created ponds (Palustrine Aquatic Bed), although
there were also some wetlands created in an area
that was formerly riparian (Figure 3).
Table 3. Wetland and riparian acreage for
theA16 reach near Columbus.
NWI Wetland or Riparian Type
1950
1976
1996
2001
Palustrine Aquatic Bed
25.4
23.8
31.0
39.0
Palustrine Wetland Total
375.4
339.3
353.6
360.2
Riverine Flowing
1149.8
934.3
1009.5
887.2
Riverine Bank
363.4
702.8
436.2
654.7
Riverine Wetland Total
1513.3
1637.2
1445.7
1541.9
Wetlands Total
1888.7
1976.5
1799.3
1902.1
Riparian Total
1563.3
1818.8
1874.2
1856.0
Wetland and Riparian Total
3452.0
3795.3
3673.5
3758.1
Table 4. Wetland and riparian acreage for the D6 reach near Glendive.
NWI Wetland or Riparian Type
1950
2001
Palustrine Aquatic Bed
97.7
Palustrine Wetland Total
316
441
Riverine Flowing
1104.9
1203.1
Riverine Bank
1349.5
730.9
Riverine Wetland Total
2454.4
1934.1
Wetlands Total
2770.4
2375.2
Riparian Total
2004.6
1871.5
Wetland and Riparian Total
4775.0
4246.7
Figure 2. Habitat change in the Yellowstone River reach A16 near Columbus from 1951 to 2001.
6
V
Figure 3. 1950 and 2001 mapping near Glendive.
There is little published research on riparian
wetlands and how they respond to river hydrology
or created structures like bridges or rip-rap. There
is virtually no research on undammed rivers in arid
environments like the Yellowstone River. Flood
events have been recognized as critical in creating
some wetlands, like willow sandbars in the well
publicized large discharge of water into the Grand
Canyon in Arizona (Stevens et al. 2001). However,
new fluvial marshes developed with reductions in
flood frequency and sediment deposition in the
same area (Stevens et al. 1995). In humid areas
lower peak flows and higher minimum flows results
in the succession of herbaceous wetlands to
wooded wetlands (Toner and Keddy 1997). High
flows will scour new channels; many of our
wetlands were eventually found in these locations
after they aged. High flows can also destroy
wetlands by filling them with new sediment. River
ice scour has also been recognized as an important
factor in structuring woody vegetation in Montana's
riparian areas (Smith and Pearce 2000) and
probably affects other wetland types too.
Created structures affect wetlands but off-site
impacts downstream were impossible to determine
with our limited sample. The reduction of sediment
with extensive rip-rap may affect wetlands as
would streamlining channels for bridges or blocking
river migration with levees.
Peak stream flow in the Yellowstone River has
shown a pattern of relatively little alteration near
Billings (Figure 4) compared to a steady decline in
peak discharge over time downstream at Sidney
(Figure 5). All photo series had fairly substantial
peak flow events within five years of the photo
year (Table 2). Large flows and ice movement
likely scour vegetation and create Riverine bank
and other wetlands.
USGS
USGS 06214500 Yellowstone River at Billings MT
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Figure 4. Annual peak Yellowstone River flows at Billings MT near study reach A16.
SUSGS
USGS 06329500 Yellowstone River near Sidney MT
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Figure 5. Annual peak Yellowstone River flows at Sydney MT near study reach D6.
Government Land Office Survey
Notes Analysis
GLO surveyors recorded water and general
vegetation types like "cottonwood forest" or
"willow shrubs" along the section lines they
established. We grouped these into types that
corresponded with our mapped types and
compared their respective lengths (Table 5). The
water type is almost double in the GLO notes
compared to our 2001 mapping, primarily due to
one section line which then ran largely down the
river (Figure 6). The GLO notes ranged from 1878
- 1904 and the surveys were completed during
several different months. This is a relatively small
sample so the results are not as important as is the
fact that there is early settlement vegetation
information available and that it is relatively easy to
extract and compare to current conditions (although
wetland types are not distinguished).
Table 5. Length (m) of vegetation types compiled
from GLO survey notes and 2001 mapping.
GLO
2001 Mapping
Shrub
670
1055
Forested
2538
3169
Water
3763
1978
Other
28805
29547
Crosswalk Between NRCS and
USFWS Cover Types
Two related USFWS mapping systems, Western
Riparian System (USFWS 1997) and National
Wetlands Inventory (NWI) (Cowardin et al. 1979),
are crosswalked with the Natural Resource
Conservation Service (NRCS) land use types
(Table 6) and vegetation cover types (Table 7) used
in other mapping in the Yellowstone River riparian
corridor. In the NWI system (Cowardin et al. 1979)
wetlands are defined as:
9
Figure 6. Section lines coded from GLO survey notes and 2001 mapping.
". . . lands transitional between terrestrial
and aquatic systems where the water
table is usually at or near the surface or the
land is covered by shallow water.
For the purposes of this classification
wetlands must have one or more of
the following three attributes: (1) at least
periodically, the land supports
predominantly hydrophytes [wetland
plants], (2) the substrate is predominantly
undrained hydric soil, and (3) the substrate
is nonsoil [does not support vegetation] and
is saturated with water or covered by
shallow water at some time during the
growing season of each year."
The Western Riparian System (USFWS 1997)
defines riparian as:
". . . plant communities contiguous to and
affected by surface and subsurface
hydrologic features of perennial or
intermittent lotic [flowing] and lentic [still]
water bodies (rivers, streams, lakes or
drainage ways). Riparian areas have one
or both of the following characteristics: 1)
distinctly different vegetative species
than adjacent areas, and 2) species similar
to adjacent areas but exhibiting more
vigorous or robust growth forms. Riparian
areas are usually transitional between
wetland and upland."
By definition, riparian types are not wet enough for
a long enough period of time to be classified as
wetlands. True wetlands will be mapped as
wetlands even if they occur within riparian areas.
Therefore, many of the NRCS types used in the
riparian mapping could crosswalk to either system
10
depending on site hydrology. Within a specific
NRCS type there could be substantial differences in
type characteristics (e.g. vegetation composition)
reflected in the range of the possible USFWS
classification types. The NRCS types are broader
concepts, so there will typically be several USFWS
types nested within each NRCS type.
Both USFWS classification systems are
hierarchical with several levels of detail that can be
applied as desired. The minimum mapping standard
is classification to all three of the following levels:
System, Subsystem (where applicable), and Class
(USFWS 2004) with hydrologic and special (i.e.
beaver, farmed, excavated, etc.) modifiers often
applied to NWI mapping. Subclasses can refer to
more specific vegetation type (i.e. Cottonwood or
Mixed Deciduous in the riparian classification) but
are often beyond what can be interpreted from the
aerial imagery.
Table 6. Crosswalk of NRCS land use cover types with USFWS wetland and riparian types.
NRCS Land Use/Cover
Type:
NWI types:
Riparian types:
(CI) Cropland - Irrigated/sub-
irrigated (includes fallow,
residue)
Generally not wetlands,
although small wetlands of
any type could occur within.
Not mapped as riparian unless
there are virtually no land
improvements and only
grazing, then probably will be
Lotic Emergent (RplEM).
(C2 ) Cropland - Non-irrigated
(includes fallow, residue)
(C3 ) CRP (may be confused
with pastureland or rangeland)
(Pl)Pastureland-
Irrigated/sub-irrigated
(P2) Pastureland - Non-
irrigated (may be confused with
CRP or rangeland)
(R) Rangeland - native (may be
confused with pastureland or
CRP)
(F) Forest land (>25% canopy,
10% stocking for coniferous or
deciduous forest)
Must meet the 30% canopy
cover limit to be mapped as
forest, probably intermittently
flooded (PFOJ), otherwise
Scrub-Shrub (PSSJ). Most of
these areas are likely not
wetlands but are riparian
types.
Must meet the 30% canopy
cover limit to be mapped as
forest (RplFO), otherwise
Scrub-Shrub (RplSS).
(U) Urban Buildup (use NRI
density rules)
N/A
N/A
(T) Rural Transportation
(corridors of significant width)
Major rural road and RR rights-
of-way
N/A
N/A
(B) Barren/Disturbed land
N/A
N/A
11
Table 6. Continued.
NRCS Land Use/Cover
Type:
NWI types:
Riparian types:
(Wl) Water Bodies
Palustrine, if vegetated,
probably only Emergent
Vegetation permanently
flooded (PEMH) or aquatic
bed (PABH). With <30%
vegetation cover, Class would
be based on bottom substrate:
Unconsolidated Bottom
(PUBH), Rock Bottom
(PRBH), or Unknown Bottom
(POWH).
Would fall under the wetland
classification.
(W2) Perennial rivers/streams
> 66 feet wide
Riverine Upper and Lower
Perennial with Unconsolidated
Bottom (R2UBH, R3UBH) or
Aquatic Bed (R2ABH,
R3UBH) the most common
Classes. Subclass either
Vegetated or based on
substrate (e.g. sand).
Would fall under the wetland
classification.
(Ol) Other Rural Land (not
cropland or urban build-up)
N/A
N/A
(02) All other land not as above
(describe in notes)
Could be anything.
Could be anything.
12
Table 7. Crosswalk ofNRCS vegetation cover types with USFWS wetland and riparian types.
NRCS Type:
NWI types:
Riparian types:
(t) Closed canopy tall woody:
Mixed Deciduous Tree > 25%
canopy and > 4 meters tall,
single stemmed
Palustrine Forested (PFO),
temporarily flooded water
regime is the most common
(PFO A), Broad-Leaved
Deciduous Subclass (PFOAl)
Riparian Lotic Forested
(RplFO), Deciduous Subclass
(RplF06)
(s) Closed canopy short woody:
Mixed Deciduous Shrub >25%
canopy and < 4 meters tall,
multi-stemmed
Palustrine Scrub - Shrub (PSS),
temporarily or seasonally
flooded water regime are the
most common (PSS A or
PSSC), Broad-Leaved
Deciduous Subclass (PSSAl or
PSSCl)
Riparian Lotic Scrub - Shrub
(RplSS), Deciduous Subclass
(RplF06)
(rl) Open canopy tall woody:
Mixed Deciduous Tree 5-25%
canopy and > 4 meters tall,
single stemmed
(pi) Open canopy short woody:
Mixed Deciduous Shrub 5-25%
canopy and < 4 meters tall,
multi-stemmed
(p2) Open canopy short woody:
Semi-Deciduous Shrub 5-25%
canopy and < 4 meters tall,
multi-stemmed
If trees and shrubs are more
than 30% canopy cover
together then this type would be
Palustrine Scrub - Shrub (PSS),
if not then typed for the
dominant Class below the tree
canopy, probably Palustrine
Emergent (PEM). Temporarily
flooded water regime is the
most common (PSSA), Broad-
Leaved Deciduous Subclass
(PSSAl)
If trees and shrubs are more
than 30% canopy cover
together then this type would be
a Riparian Lotic Scrub - Shrub
(RplSS), Deciduous Subclass
(RplSS6), if not then probably
Riparian Lotic Emergent
(RplEM).
(r2) Open canopy tall woody:
Mixed Coniferous Tree 5-25%
canopy and > 4 meters tall,
single stemmed
If trees and shrubs are more
than 30% canopy cover
together then this type would
classify as a Palustrine Scrub -
Shrub (PSS), if not then
probably Palustrine Emergent
(PEM) or other dominant Class
below the tree canopy.
Temporarily flooded water
regime would be the most
common (PSSA), Needle-
Leaved Evergreen Subclass
(PSSA3)
If trees and shrubs are more
than 30% canopy cover
together then this type would
classify as a Riparian Lotic
Scrub -Shrub (RplSS),
Deciduous (RplSS6),
Evergreen (RplSS7) or Mixed
(RplSSS) Subclass, if not then
probably Riparian Lotic
Emergent (RplEM).
(hi) Herbaceous/Graminoid,
mixed: actively growing - wet,
<5% woody canopy
Palustrine Emergent (PEM),
Water regime is most
commonly temporarily
(PEMA), seasonally (PEMC),
or semi-permanently flooded
(PEMF). Persistent (PEMAl)
or Nonpersistent (PEMA2)
vegetation Subclass
This type is probably all
wetland.
13
Table 7. Continued.
NRCS Type:
NWI types:
Riparian types:
(h2) Herbaceous/Graminoid,
mixed: non-actively growing -
dry, < 5% woody canopy
(h3) Herbaceous/Graminoid
Complex: (hi) + (h2), < 5%
woody canopy
Palustrine Emergent (PEM),
Water regime would be most
commonly temporarily
(PEMA). Persistent (PEMAl)
Subclass.
Riparian Lotic Emergent
(RplEM)
(cl) Crop cover (tilled row and
close-grown crops, fallow,
residue, idle)
(c2) Crop cover (perennial, not
tilled); hayland
If vegetated wetland then
Palustrine Emergent with
Farmed modifier (PEMf),
Water regime would probably
be temporarily (PEMAf).
Not mapped as riparian unless
there are virtually no land
improvements and only light
grazing.
(a) Artificial cover (build-up,
commercial, paved areas, etc)
These would not be wetlands.
Would not meet the riparian
definition - must be vegetated.
(b) Barren (flood deposits,
saline areas, pits, mines,
disturbed areas)
If these are wetlands then
most would probably be
Palustrine Unconsolidated
Shore with a temporarily
(PUSA), seasonally (PUSC),
or semi-permanently (PUSF)
flooded water regime.
Subclass either Vegetated or
based on substrate (e.g. sand).
There could possibly be other
classes depending on the
specific circumstances.
Would not meet the riparian
definition - must be vegetated.
(w) Water (includes exposed
low- water riverwash in primary
channel)
If within the river channel
then Riverine Lower Perennial
with Unconsolidated Shore
(R2US), Unconsolidated
Bottom (R2UB), or Aquatic
Bed (R2AB) the most
common Classes. Subclass
either Vegetated or based on
substrate (e.g. sand). The
exposed riverwash (if large
enough to map) would be
Palustrine Unconsolidated
Shore with a seasonally
(PUSC), or semi-permanently
(PUSF) flooded water regime.
Subclass either Vegetated or
based on substrate (e.g. sand).
Would fall under the wetland
classification.
14
Conclusions and Recommendations
The five series examined (1930's, 1950's. 1970's,
1990's and 2001) were generally acceptable for
wetland mapping, however, the 1950's photos had
issues with quality and timing. The quality was
significantly lower than all the other series,
probably resulting in lower accuracy, especially
with accurately assigning vegetation types. A more
significant issue was the mid-May acquisition of the
A16 reach compared to the late summer timing of
all other photo series. The associated high water
levels in A16 may have covered some low
Palustrine wetlands. Water levels were especially
high even for this date and magnified the problem.
Any future wetland change project should make
sure that the dates of imagery are comparable.
Even with the problems in the baseline 1950
imagery there were a few clear trends apparent.
Created ponds have increased in both reaches but
especially in the more developed reach near
Glendive (D6). Wetland acreage has decreased in
both reaches with a greater decrease in D6. The
less developed A 16 reach was mapped on four
dates of aerial photography; wetland totals varied
within about a 10% range. The Riverine type
varied the most, probably due to water levels and
scouring from events within a few years previous
to the photo date. Large peak flows are important
in creating wetland sites. There may be more
wetland change downstream than upstream since
peak flows have diminished more downstream.
Most wetlands are within the riparian corridor:
primarily 1) within the channel (Riverine System),
2) close to the channel (Palustrine System), or 3) in
old channels or oxbows (Palustrine System). The
riparian corridor is extremely dynamic, as are the
associated wetlands. Few wetlands persist longer
than a few decades; many are quite ephemeral and
may persist only a few years. Wetland type within
an individual site may also change quickly. Wetland
change is best viewed as total acreage amounts in
broad classes over the time period considered
instead of tracking individual wetland areas.
The Government Land Office survey field notes
can be used to compare riparian vegetation
composition from early settlement times to current
conditions although wetland types are not
distinguished.
The NRCS land use and cover classification
systems were crosswalked to USFWS wetland and
riparian types. Some had a simple relationship but
most NRCS types could be one of many USFWS
types. The NRCS mapping also has a several acre
minimum mapping unit, which is too large to
identify the often small wetlands areas.
15
References Cited
Cowardin, L.M., V. Carter, EC Golet, and E.T.
LaRoe. 1979. Classification of Wetlands and
Deepwater Habitats of the United States. U.S.
Department of the Interior, Fish and Wildlife
Service, Washington, D.C FWS/OBS-79/31.
Smith, D.G. and CM. Pearce. 2000. River Ice and
Its Role in Limiting Woodland Development on a
Sandy Braid-Plain, Mile River, Montana. Yfet-
lands Vol. 20(2) pp. 232-250.
Stevens, Lawrence E., Schmidt, John C, Ayers,
Tina J., Brown, Bryan T. 1995: Flow Regulation,
Geomorphology, and Colorado River Marsh
Development in the Grand Canyon, Arizona.
Ecological Applications: Vol. 5, No. 4, pp.
1025-1039
Stevens, Lawrence E., Ayers, Tina J., Bennett,
Jeffery B., Christensen, Kerry, Kearsley,
Michael J. C, Meretsky, Vicky J., Phillips,
Arthur M., Parnell, Roderic A., Spence, John,
Sogge, Mark K., Springer, Abraham E., Wegner,
David L. 2001 : Planned Flooding And Colorado
River Riparian Trade-Offs Downstream From
Glen Canyon Dam, Arizona. Ecological Appli-
cations: Vol. 11, No. 3, pp. 701-710
Toner, M. and P. Keddy. 1997: River Hydrology
And Riparian Wetlands: A Predictive Model For
Ecological Assembly. Ecological Applications:
Vol. 7, No. 1, pp. 236-246
U.S. Fish and Wildlife Service. 1997. A System
for Mapping Riparian Areas in the Western
United States. U.S. Department of the Interior,
Fish and Wildlife Service, Lakewood, CO. 15 p.
U.S. Fish and Wildlife Service. 2004. National
Standards and Quality Components For Wet-
lands, Deepwater and Related Habitat Mapping.
U.S. Fish and Wildlife Service, Branch of
Habitat Assessment, Arlington, VA. 1 8 pp.
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